56 +14 = 70, meaning we have a 14 byte overhead. I did some research on this and I ended up going to my book self and dug out the SQL Server 2012 Internals text book, the 14 byte overhead is needed for “the actual pointer to the file, page, and row in tempdb which needs 8 bytes and 6 bytes are needed to store the XSN” (Chapter 13. Page 823)